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S&S Swan Maintenance - Swan 47 fuel tanks
26 April 2015 - 21:40
#1
Join Date: 29 January 2007
Posts: 1018

Swan 47 fuel tanks
Dear All,

onboard Vanessa there are two (standard equipment) fuel tanks, and there is no connection between the two of them, so I have to fill them separately; I am thinking to get a link between the two of them.

Any suggestion/objection?

Many thanks, and Fair winds!

matteo (47/069 Vanessa)

Port Tank

27 April 2015 - 16:07
#2
Join Date: 02 January 2008
Posts: 1547

Dear Matteo
Assume you would prefer an arrangement enabling both tanks to be filled from both deck connections? This requires that you find a route for a connecting filling hose, and add shut-off valves for each tank so you can direct the fuel to the tank of your choice, and prevent cross-flow when heeled.
Kind regards
Lars

27 April 2015 - 19:21
#3
Join Date: 30 January 2007
Posts: 461

Dear Lars,
Just a naive question from a curious person: which is the reason for preferring to avoid cross-flow? And then: how are configured the feed pipings from two independent tanks to the engine?
Thank you in advance.
Daniel, 411/004

27 April 2015 - 19:43
#4
Join Date: 29 January 2007
Posts: 1018

I always LOVE Daniele's questions!

Fair winds

matteo (47/069 Vanessa)

27 April 2015 - 21:09
#5
Join Date: 02 January 2008
Posts: 1547

Dear Daniele and Matteo
The Swan 411 has one fuel tank like the Swan 38, but if there are two or more tanks, they are connected to a fuel valve chest, usually located below the floorboards near the tanks. From the chest there is a single feed and return line to the engine.
Diesel engines cool the injection pump by circulating a liberal amount of fuel through the pump, and the excess is led back through the return line.
By turning the chest valves the captain chooses which tank to use, and where the fuel return should go. Usually it is the same tank, but it is possible to slowly move fuel to another tank by directing the return to it.
The recommendation is to keep only one tank open at a time, if several are open there may be cross-flow when the yacht heels.
If fuel can flow from the tank on the high side to the lower tank when heeled, the lower tank may end up overfilled, and overflow though the air vent depending on its location.
The tank on the high side may end up empty, and all this will certainly surprise the unaware captain thinking that he knows how much fuel there is in each tank.
The same refers for water tanks when there are several of them, but they do not have return lines.
Kind regards
Lars

27 April 2015 - 22:16
#6
Join Date: 01 March 2007
Posts: 147

Dear Matteo,

We have a similar arrangement as described by Lars. It is amidships at the base of the companionway steps. In the photograph we are using the starboard tank and returning there too.
The only time I have wanted to move fuel around was to allow filtering dirty fuel bought in France and then cleaning tanks.
Best
Rob
Sarabande 47/029

27 April 2015 - 22:32
#7
Join Date: 29 January 2007
Posts: 1018

Dear Daniele, Lars and Rob,

thanks!

Fair winds

matteo (47/069 Vanessa)

27 April 2015 - 23:09
#8
Join Date: 23 October 2011
Posts: 150

Dear All, onboard Vanessa there are two (standard equipment) fuel tanks, and there is no connection between the two of them, so I have to fill them separately; I am thinking to get a link between the two of them. Any suggestion/objection? Many thanks, and Fair winds! matteo (47/069 Vanessa)

On board Grampus I have three tanks, two of them on both sides in the bunks of the settee, and the third tank centrally located down in the bilge under the floor board abaft of the dining table.
Each tank is about 140 liters, the central tank being slightly smaller(total fuel around 400 liters).
There is a pump, centrally located, which feeds, by means of a set of cocks, the central tank from both side tanks.
I have this habit of keeping always one side tank full with its cock shut; When I refuel, I usually refuel only one side tank(plus the central tank and the fuel pump on). After refuelling I work in reverse the cocks,so that the tank just refilled will be locked this time. I believe that this way of operating is better, but I am not sure...
I believe it is better to keep one tank always full, with the exception of long transfers. There will be less condensation. And more safety in case of filthy fuel
As the Professor has already pointed out it is safer to have the tank on the lee locked, although I have not noticed in my case any unconvenient not doing this. Whatever the solution, I appreciate having two separate intakes of fuel on deck.
I believe that in my case, having a dissalator, I need less water capacity and therefore I can deserve more fuel in the tanks, compared to other layouts.
It would be good to know from Lars if this solution with three tanks in the 47 has been an original option from Nautor.
Thank you and f.w.
Matteo 45
(grampus 47/016)

28 April 2015 - 13:33
#9
Join Date: 02 January 2008
Posts: 1547

Dear Matteo 45
Thank you for the information.
Using the system as described you take care that the fuel in each tank is replaced regularly, which is good.
If the central tank and one wing tank are kept open at the same time, the effect of heeling is small as they are close together.
Would suggest that you compare the tank cover details on the central tank with those of the others - if identical the tank is original.
Kind regards
Lars

29 April 2015 - 14:55
#10
Join Date: 23 October 2011
Posts: 150

Dear Lars
Thank you very much.
Your suggestions are always very logical. The three tanks have been installed in the same time because the look quite similar. There are digits engraved on top of them, curiously indicating the volume in gallons. I do not know if these numbers refer to imperial or us gallons (although I guess they should be imperial because the first flag of the boat was UK). It is not so simple to know the exact volume because I do not know the internal height of the outcome piping.
In the other case of only two tanks, I would suggest to check at how many Racor prefilters are installed and speak with a mechanician, maybe he can agree to install a piping with its cocks to level the two tanks closing the intake of the filters and opening the new bypass. Anyway the dimension of this piping is very small and it can take time for it.
thank you
Matteo 45
Grampus 47/016

29 April 2015 - 21:18
#11
Join Date: 02 January 2008
Posts: 1547

Dear Matteo
The numbers on top of the tanks are US gallons. The total capacity for the two standard fuel tanks is 55.5 US gallons, is this close to your numbers? This corresponds to 210 liters.
Kind regards
Lars

30 April 2015 - 14:05
#12
Join Date: 23 October 2011
Posts: 150

Dear Matteo The numbers on top of the tanks are US gallons. The total capacity for the two standard fuel tanks is 55.5 US gallons, is this close to your numbers? This corresponds to 210 liters. Kind regards Lars


Dear Lars,
nothing escapes Professor Lars!
Indeed , the numbers engraved on the lids of the two side tanks show 28,3 gallons, which means, dealing with U.S. gallons, 107,13 liters, and a confirmed total of 214 liters for the two tanks.
I was wrong in considering the capacity of 140 liters for each one!
This is because when the meter of that tank shows that it is completely empty, after refilling,the consumption from the gas station shows 130-150 Liters.
This happens quite probably because the exit cock is open and in the meantime the central tank has been partially reloaded by gravity !
In those cases in which I switch on the fuel pump,(from the side tank to the central tank)then I reach more, around 180-200 from only one side deck inlet, until the central meter shows it is full.
Then the total capacity of my tanks should be around 320 liter..
Thank you very much Lars!
You are exceptional!
Matteo45
Grampus 47/016

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